linux-kernel - [PATCH] random: replace use of system_unbound_wq with system_dfl

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251030155728.271373-1-marco.crivellari@suse.com>
Date: Thu, 30 Oct 2025 16:57:28 +0100
From: Marco Crivellari <marco.crivellari@...e.com>
To: linux-kernel@...r.kernel.org
Cc: Tejun Heo <tj@...nel.org>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Marco Crivellari <marco.crivellari@...e.com>,
	Michal Hocko <mhocko@...e.com>,
	Theodore Ts'o <tytso@....edu>,
	"Jason A . Donenfeld" <Jason@...c4.com>
Subject: [PATCH] random: replace use of system_unbound_wq with system_dfl_wq

Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.

This lack of consistency cannot be addressed without refactoring the API.

system_unbound_wq should be the default workqueue so as not to enforce
locality constraints for random work whenever it's not required.

Adding system_dfl_wq to encourage its use when unbound work should be used.

The old system_unbound_wq will be kept for a few release cycles.

Suggested-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>
---
 drivers/char/random.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index b8b24b6ed3fe..92ec34a303c9 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -259,8 +259,8 @@ static void crng_reseed(struct work_struct *work)
 	u8 key[CHACHA_KEY_SIZE];
 
 	/* Immediately schedule the next reseeding, so that it fires sooner rather than later. */
-	if (likely(system_unbound_wq))
-		queue_delayed_work(system_unbound_wq, &next_reseed, crng_reseed_interval());
+	if (likely(system_dfl_wq))
+		queue_delayed_work(system_dfl_wq, &next_reseed, crng_reseed_interval());
 
 	extract_entropy(key, sizeof(key));
 
@@ -741,8 +741,8 @@ static void __cold _credit_init_bits(size_t bits)
 
 	if (orig < POOL_READY_BITS && new >= POOL_READY_BITS) {
 		crng_reseed(NULL); /* Sets crng_init to CRNG_READY under base_crng.lock. */
-		if (static_key_initialized && system_unbound_wq)
-			queue_work(system_unbound_wq, &set_ready);
+		if (static_key_initialized && system_dfl_wq)
+			queue_work(system_dfl_wq, &set_ready);
 		atomic_notifier_call_chain(&random_ready_notifier, 0, NULL);
 #ifdef CONFIG_VDSO_GETRANDOM
 		WRITE_ONCE(vdso_k_rng_data->is_ready, true);
-- 
2.51.0